Senin, 01 Februari 2010

Batuan di Permukaan bumi


A. Struktur Lapisan Litosfer
Litosfer adalah lapisan kulit bumi paling luar berupa batuan padat. Litosfer tersusun atas 2 lapisan yaitu kerak dan selubung yang tebalnya sekitar 50-100km. litosfer merupakan lempeng yang bergerak sehingga dapat menimbulkan pergeseran benua.
B. Batuan Pembentuk Kulit Bumi
Batuan / Batu adalah sejenis bahan yang terdiri daripada mineral dan dikelaskan menurut komposisi mineral. Pengkelasan ini dibuat dengan berdasarkan : Bagian luar bumi tertutupi oleh daratan dan lautan dimana bagian dari lautan lebih besar daripada bagian daratan. Akan tetapi karena daratan adalah bagian dari kulit bumi yang dapat kita amati langsung dengan dekat maka banyak hal-hal yang dapat pula kita ketahui dengan cepat dan jelas. Salah satu diantaranya adalah kenyataan bahwa daratan tersusun oleh beberapa jenis batuan yang berbeda satu sama lain.

Minggu, 03 Januari 2010

Igneous Rock Clasification

Mineral Percent Abundance Chart

     The table at the top of the page is read vertically, from zero% at the bottom to 100% at the top (scale on left and right sides). For example, the composition of the rock on the farthest right side of the chart is (bottom up) about 92% olivine, and the remaining composition to the top about 8% pyroxene.

Alphabetical List Of Igneous Rock

 Below is an alphabetical list of igneous rocks. If you know the name of a rock and want to learn more about it, clicking on the name will take you to a picture and a description. Names that are not linked are ones for which pictures/descriptions are not yet available.


   Click image for larger version.      Igneous rock evolution does not just happen anywhere. It takes special plate tectonic conditions. A basic understanding of plate tectonics is necessary here, and if you are unfamiliar with the ideas go to this link for a quick, simple introduction.


One of the most important ideas geology has discovered is that igneous rocks evolve. That the earth began with a composition similar to that of the moon, that is, composed mostly of an mafic/ultramafic parent rock, and from that simple beginning all the other rocks have evolved through a sequence of fractionation processes. It is a core concept essential to understanding the Earth's evolution that is explored in the Wilson Cycle and a Plate Tectonic Rock Cycle.


The inside of the earth is very hot - hot enough to melt rocks. And the deeper you go the hotter it gets. Below the surface the molten rock is called magma; at the earth's surface it becomes lava, although nothing has changed except the name.
     The fresh magma is white hot, brillant enough that you would have trouble looking at it. But as it cools it turns yellow, and then various shades of red. Eventually it cools enough to solidify completely and form an igneous rock, such as the granite and basalt below. Granite and basalt are the two most abundant igneous rocks at the earth's surface.

Magma Types

     Igneous rocks come in four basic varieties, ultramafic, mafic, intermediate, and felsic (red text is clickable to samples). These rocks are each composed of different suites of minerals, and are derived from magmas and lavas which have different properties.

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